Process for machining porous metals



IMPREGNA TED H. L. WHEELER, JR

PROCESS FOR MACHINING POROUS METALS Filed July 13, 1950 M 14C Hl/VEDJNVENTOR. -Wha E 1 e 1", LT n nr'raz/vs rs W m a Dec. 29, 1953 Hurry LBY m T M e h P m MHCf/l/VED BL ANK NOT IMPEEGNHTED BL ANK IMPREGNH TEDPatented Dec. 29, 1953 PROCESS FOR MACHINING POROUS METALS Harry LindsayWheeler,

assignor to the United represented by the Seer Application July 13,1950, Serial No.

mense quantities of heat, thus the metal wall is isolated from theregion of intense heat and is protected against burn-out. Thisphenomenon known in the art as sweat-cooling Jr., La

etary of the Canada, Calif., of America as Army States materials such asstainless steel, and chromium, nickel, and olybdenum alloys in general,which are essentially noncorrosive, cannot be etched satisfactorily. Mymethod eliminates these dise usual machining operations to be employedwithout destroying the porosity of the stock.

It is a broad Without porosity thereof.

It is a still more specific object of my invenon to provide mat wherein:is a porous metal blank, not impregspecification and Figure 1 nated.

line 2-2 of Figure 1. blank not impregnated,

Figure 4 illustrates the blank of Figure 1 after it has been impregnatedand Figure 5 is the blank of Figure 4 after it has been machined.

In carrying out of other solvents.

have found that sodium chloride or other metallic salts (e. g.,potassium chloride, or a eutectic mixture of salts such as required.With oxalic acid, a ween ZOO-260 F. is sufficient. After the porousnaterial is impregnated and allowed to cool in air, machining, shaping,milling, grinding, drill- .ng or other operations may be carried on inthe usual way. It is essential that sharp tools be used and heavy cutsavoided. No cutting compounds should be used..

After the machining operations, the filler may be removed from thespecimen by dissolving in water or by the use of steam. Oxalic acid,decomposes at 125 0., maybe removed by heattemperature be- It should benoted that when; sodium chloride or other salt Whose meltingpOint-ishigher than that of soft or silver solder is usedrtheimpregnated porous material may be soldered toa solid, section of metal.

Fahrenheit, cooling the said metal whereby the said oxalic acidsolidifies. metal, and removing the said oxalic acid by heat: ing.

described above 2. A method of protecting the porosity of metalsmachined for use in sweat-cooling apparatus which comprises, filling thepores of said metal with fluid oxalic acid at a temperature between200-260" F., cooling the said metal whereby the oxalic acid solidifiesWithin the pores thereof to present a solid surface for machining,machining said metal, andremoving the said oxalic acid from the-pores ofsaid metal by heating after machining.

3. A method of preserving the porosity of porous metals to be machinedfor use in sweatcooling apparatus which comprises, submerging the metalin a molten bath of oxalic acid for 20 minutes and .with' a betweenZOO-260 R, cooling the impregnated metal to present a smoothsurface formachining, machining said metal, and dissolving the impregnatingmaterial from the pores of the metal after machining, with heat at C.

HARRY LINDSAY WHEELER, JR.

in the filel of this patent J'NITED STATES PATENTS Number Name Date1,683,437 Batie Sept. 4, 1928 2,047,555 Gardner July 14, 1936 2,159,391Martin et a1 May 23, 1939 2,304,166 Hatfield Dec. 8, 1942 2,446,672 SirpAug. 10, 1948 2,462,045 Wulfi Feb. 15, 1949 FOREXGN PATENTS NumberCountry Date 455,077 Great Britain Oct. 13, 1936

1. A METHOD OF MACHINING A POROUD METAL FOR USE IN SWEAT-COOLINGAPPARATUS WHICH COMPRISES FILLING THE PORES OF THE SAID METAL WITH FLUIDOXALIC ACID AT A TEMPERATURE BETWEEN 200-260 DEGREES FAHRENHEIT, COOLINGTHE SAID METAL WHEREBY THE SAID OXALIC ACID SOLIDIFES, MACHINING THESAID METAL, AND REMOVING THE SAID OXALIC ACID BY HEATING.